Pressure washers are often used to provide a substantially constant flow of liquid at an increased pressure to a work surface or object for cleaning of that surface or object. Pressure washers often include a pump for increasing the pressure of liquid provided therefrom, a path for flowing from the pump, and a wand or similar structure that can be held by the user to direct the relatively high pressure flow to the object or surface to be cleaned.
Many types of nozzles for use with pressure washers are known in the art. Some nozzles provide output flow in a single cylindrical stream, multiple parallel streams, planar fluid flows, or many other geometries. Further, some nozzles alter the pressure of the fluid flowing therefrom by dramatically reducing or increasing the cross-sectional area of the output aperture, which makes different nozzles useable for different functions.
It is known that fluid backpressure upstream of a nozzle is important when mixing fluid from a pressure washer for simultaneously applying pressurized fluid and cleaning solution to both mechanically agitate the surface to be cleaned and additionally provide soap to the surface for further removal of dirt and debris. It is known that a large increase in system pressure (due to a reduction of output flow from a nozzle) may reduce or eliminate the entry of cleaning solution into a fluid flow due to a reduction in differential pressure across a venturi that is connected to the source of cleaning solution.
Nozzles that adjust the geometry of spray flow from the nozzle are known in the art. These nozzles often cause the backpressure to vary as the geometry is changed because the nozzles vary the size and shape of the outlet aperture of the nozzle in order change the flow geometry. The change in the cross-sectional area additionally causes changes to the system pressure within the pressure washer due to the change in output flow rate from the nozzle, which may alter the amount or eliminate the flow of cleaning solution into the fluid flowing through the nozzle.